Inverter integrated type electric compressors, in which an inverter device is integrally installed in a compressor housing, have been employed as the compressors of vehicle air conditioners for hybrid cars, electric automobiles, and the like. The inverter device converts high-voltage DC power supplied from a power source (battery) installed in a vehicle to three-phase AC power having a predetermined frequency based on control signals from an upper-level control device, and applies this three-phase AC power to the electric motor, thereby rotating the electric motor at a required rotational speed and driving the compressor.
The inverter device is provided with a board, on which a switching circuit having a plurality of semiconductor devices, a control circuit thereof, and so forth are mounted, and electrical components of a high-voltage system, such as a smoothing capacitor, an inductor coil, and so forth, and, although the inverter device is installed so as to be accommodated in an inverter housing portion, it is not resistant to moisture or the like. Because of this, the inverter housing portion has a cover piece with which the inverter housing portion forms an airtight structure. Known airtight seals employed in this cover piece include an O-ring, a gasket, a sealing material in which a rubber material is provided around a core wire, which are disclosed in Patent Literature 1, a liquid gasket, which is disclosed in Patent Literature 2, or the like.